In this problem we wish to study practical applications of environments. Consider the iterative definition for the Fibonacci function:

(define fib-iter

(lambda (int acc1 acc2)

(if (= int 1)

acc2

(fib-iter (sub1 int) acc2 (+ acc1 acc2)))))

Write a definition for the Fibonacci function using letrec to make the iteration local to the fib function.